The present invention relates to an aircraft-mounted telescope which is suspended on one side of a bulkhead or partition wall of the fuselage and is mounted for rotation or swing about two axes.
Such a telescope is known, for example, from "Sky and Telescope", November 1976 issue, pages 327 to 331. That telescope is a 90-cm infrared telescope which permits observations of astronomical objects in a spectral region in which ground-mounted observations cannot be performed, due to attenuation in the earth's atmosphere.
This known apparatus can be tilted or swung through an angular range of about 4.degree. with respect to the longitudinal axis of the airplane and is mounted for rotation within an angular range of about 40.degree. in elevation, i.e., about an axis parallel to the flight-direction. The mounting consists of a gas-pressure bearing in the form of a ball-and-socket joint which is integrated in the partition wall which separates the observation space (which is open in viewing direction and is taken up by the telescope) from the operator's control space (which is kept at nominal pressure).
The known apparatus is balanced with respect to its two axes by means of counterweights and therefore is inherently of relatively great weight, a factor which makes it difficult to integrate the apparatus into the somewhat labile fuselage of an aircraft.
In the known apparatus, the instrument is a reflecting telescope and the center of gravity of the tube lies in the vicinity of the primary mirror and, therefore, at the lower end of the tube. The elevation axis is through this center of gravity, and therefore a relatively large telescope-viewing window must be provided in the fuselage. Such a window is difficult to provide, due, among other reasons, to considerations of stability.